All of the above have been suggested as answers to the strange worldwide phenomenon of unusually large pieces of ice falling from clear skies.

Snyder, 52, who lives in the Cobblestone Court development near Neffsville, doesn’t know what to think.

Around noon Sunday, the behavioral health therapist was sitting in the family’s kitchen, working on a computer, when he heard a “thump” outside, he said.

His dog stood up. A neighbor’s dog started to bark.

Snyder went to the window and looked outside. There, on the ground about 60 feet away, was a round block of ice next to the pear tree. Leaves were still fluttering downward.

Silly teens must have thrown it into the yard as they drove by, he thought, and he went back to work.

But an hour later, when he went outside to take the dog for a walk, he approached the melting ice.

This time, he noticed that the milky ice had plummeted through the tree like a missile, breaking branches on its way. The largest chunk landed about 10 feet from the base of the tree; a couple of baseball-size pieces lay nearby.

It occurred to him that something strange had happened.

He brought his oldest daughter outside and called over his neighbors. “I wanted to show people so they didn’t think I was crazy,” Snyder said.

He thought he’d preserve the ice in a freezer, even though, by that time, it had been melting for an hour and had been chewed on by the dog.

Still, he estimated its weight at 10 pounds and its diameter at 8 inches — big enough to have hurt someone or damaged nearby homes and cars.

“It scares me a little, because it would easily have come through a roof,” he said.

A mysterious piece of ice falling from the sky is not a new occurrence — not even in Lancaster County.

In November 2002, a Lititz man working in his yard heard a whoosh, looked up and watched in stunned amazement as a 2-foot-long chunk of ice embedded itself in his lawn.

In an incident that made national headlines in October 2008, a 6-pound piece of ice crashed through the roof of a house in York. It shattered into pieces in a woman’s bedroom. A small piece hit the woman, giving her a bump on the forehead.

The first suspects in such cases are usually airplanes.

Lavatory holding tanks sometimes spring leaks, said Jim Peters, a spokesman for the Federal Aviation Administration. The waste seeps along the plane’s fuselage and freezes in the high-altitude air. At some point, pieces might break off and hurtle to earth.

There’s even a phrase coined for such an incident: blue ice, taken from the blue sanitizing chemical used in toilets. However, not all lavatories use the chemical and a leaking water supply could result in ice that is white.

In 2005, however, FAA put out a fact sheet that listed a number of what it called popular “myths” about material attributed to planes.

In the case of blue ice, the fact sheet says: “If any of this blue ice were to fall from an aircraft, it would melt long before it hit the ground, dissipating into minuscule droplets that are nearly invisible.”

Still, Peters contacted Snyder on Tuesday, and the FAA’s Harrisburg office was to call Snyder about examining the ice chunk he saved.

“We’d just like to know about these things,” Peters said.

Could the chunk be hail?

The ice that Snyder found fell from a clear sky, and hailstorms are formed during thunderstorms.

These space objects could send rocks to Earth as they burn up entering the Earth’s atmosphere, but it would have to be a huge ice object to survive the incredible heat from slamming through Earth’s atmosphere, he said.

Besides, lab tests on some of the large ice balls have shown them to have the makeup of terrestrial hailstones.

“It does not appear to be extraterrestrial,” Allen said.

Eric Horst, Millersville University meteorologist, said, “If it came from a clear sky, it was from an airplane.”

After a 2000 incident in which ice chunks up to 6.6 pounds pelted Spain and Italy on cloudless days for 10 days, a Spanish planetary geologist coined a new phrase and theory. Jesus Martinez-Frias called the phenomenon megacryometeors and said it happens under unusual atmospheric conditions.

A website devoted to ice-falling events is www.megacryometeors.com. Disciples of the megacryometeors theory say that there have been recorded instances of large chunks of ice falling to Earth since the 1800s, well before the creation of the modern airplane.